1. Field of the Invention
This invention relates to a wind-driven vessel which cruises by wind force energy. In particular, the invention relates to a wind-driven vessel which is driven by a windmill which normally rotates with respect to natural wind direction.
2. Description of the Prior Art
Vessels utilizing wind energy as a driving force are known, such as sailing vessels, yachts and windmill vessels. Although sailing vessels are simple in their structure, they are unable to sail against the wind direction. To the contrary, yachts which cruise by lifting force at the sails are able to move at an angle against-wind, but they are difficult to steer. Windmill vessels are driven by wind energy which is converted to rotational energy by a horizontal axis windmill or vertical axis windmill, said energy being transferred to a screw in the water, which enables the vessels to cruise against the wind.
Such prior art windmill vessels are shown in FIG. 6, in which numeral 1 is vessel body, 2 is a mast, 3 is a center board, 4 is a rudder, 5 is a link mechanism, 6 is a rotational shaft, 7 is a propeller type windmill, and 8 is an window check stabilizing plate by which a rotor of a propeller type windmill (rotational plane) is always kept in a wind direction and a rotation of the windmill is transferred to the screw (not shown) to power the vessel.
However, said windmill vessels are unable to efficiently utilize the energy of natural wind. For example, when the windmill vessel 1 cruises in a direction shown by arrow A with side winds W1, W2 as shown in FIG. 7, the vessel body receives the natural wind W1, W2 from the side when starting but receives the wind W2, W2 from a slant forward as the vessel cruises in the direction A. This is caused by an outlook wind (self cruise wind) W3, which is received by the vessel. As a result, the vessel receives the slant front winds W2, W2 caused by the mutual effect of the side natural wind W1 and the outlook wind (self cruise wind) W3 from the front. Accordingly, a rotor of the windmill 7 rotates in a direction of the slant front winds W2, W2 as an affect of window check stabilizing plate 8.
In other words, the vessel converts the energy of the slant front winds W2, W2 to a rotational energy to enable cruising. Hence, only the residual energy of W2 is utilized (i.e. the reduction in the natural wind W1 energy due to the effect of the outlook wind (self cruise wind) W3).
An additional drawback of such prior art windmill vessels is that when the windmill vessel receives the natural wind from the front of the vessel or from behind the vessel, it is unable to cruise at a speed higher than the wind velocity.